Paper machinery



Feb. 16, 1954 J. BAXTER, JR

PAPER MACHINERY Filed July 10, 1950 JOSEPH BAXTER Jr.

ATTOR N EYS Patented Feb. 16, 1954 .;2,'6.69,165 PAPERTMACHINERY ,iJo'seph aBaxter, .:'.lr., Franklin, Ohio, assignor if!) zilheiBlack-filawson ,fl mpany, Hamilton; Ohio, vazcorporationofiohio Application lTll1y"10,"1950, Serial No. 172,981

imemims. ((11.92-20) ":This invention relates 'to :apparatus and :a

method for the-treatment of paper making:stock and: other liquid slurry stocks.

Elia-invention:hasparticular relation inspaper making te the defi'bering of (the 1 stock; as: it-tomes fromthe: beater' or: other pulping apparatus, for the :purpose of effecting separation of .the indiv-idual fibers fromthe bundles or lumps of fiber in-hther pulp before .thestock is treated in a Jordan orvotherllike refiner. 'IIt is a conventionallpraotice-ito idefiberl-the stock:at this stagewzof itspreparation by a so-oalledslu'shing operation J in a jerdan,-=with=the plug backed off to-provide substantial-elearaneebetween thencutterzbarsxof thesplug andshell; 'However,-ithisiis'rnot: an efficient pro cedure, since it is :necessary 'eto athrottle *the entput in order :to hassuretan adequate period .105

treatment, and the power :requirements are accordingly relatiyelyihigh in scomparison' wwithtthfi capacity. "Furthermore, :in 2a jor'clan or other:

conventional refiner r-employing bars, disks or plates ior the :refining action, ai large portion Of the i-stook passes through the .=.channels :hetween the: cuttingwsurfaces whileronlysaes'mallr fraction ofithe' fibers: are :actually "worked on, which further reduces theaeificiencyof.such apparatus for this-.-:p,u-rpose.

".The.:presentc;invention:provides :an entirlydifi ferent type of iactionson'zthe stock; and employs a'cpair of rapidly rotating cylindrical zbrushes.

which sare .:cover.ed with rclosely spaeexi bristles andMhiclmarezarrangedzin .parallehand -close:relation ito formeamip-Ifor receiving the; stockiato :be treat-ed. In operation thetstock .islfedato ithem'ip im-a controlled. flowzsuchzzthatpitrisszall:forced to pass betweenathe s:brushes', :1and aw'ith cthe bristles thereon irelativel-y closely. arranged, uthere -.-is an effective straining iand .rdewatering 3&(3131011 asneh that sens fibers zareaconcentrated inr-azthinglayer which passes :through the .nip :of the -rbrushes Whilmtherliquid component of the stock vflows through i'the zzbristles on either side of :the nip. The thickness of this .vconcentrated ilayer edepends on both :the relativeispacing 'ofi'the' bristles onxeacn brush-and :the :eloseness 'of the brushes tozeaehcother, as wellxas von ;the speed;of irotation of'zthelbrushes and tithe-consistency -ofthezstook, and? if the 2 bristles {are :wsnficiently close and the brushes crctate at :high speed rand ,are arranged inssubstantially .jtouehing relation, athe layer-will I isnaetion -:will be :substantially uniform rfor rail 2 particles vsince there :is opportunity for ;.the stock toapass through the :device except rbyz-passagezthrough the ynipsof the :brushes.

1 Theeffectiveness. :of the :apparatusand method '-of:the1- invention is increased "by-suitable control of the'rratepi :the approach tfiow-rof the stook with respect to the rp ripheralr-speed Qfithe rotating :lorushes. Thus :if I'the :a-pproach rflow is relatively slow in :eemparison with the nbrush speed, there-will heiazisudden accelerationrofnzthe $110012 entering .the nip; 015117116 brushesgasit passes throug-hrtheanip. :Whenrtherfibers'are thus suddenlyaccelerated, and particularly withztheg acceler-ation:imparted;-by the rotatione'of h rbrush surfaces .againstvtheinertiaaofytherrelativelyslow approach *flow, r'the :fibers a a1? .a brushed outiin-the direction of .fiow through? the w ip, and there is thus' a -=teaseling-effeot lay :the: 910131011210? the ends of thebristlesagainshthe slowrmoving approach flow of the body of the stock which causes .the individualv fi'berswto be literally drawn or snatehed outmf ,-,the'..sus,pens-ion with resulting thig-hl-y effective and 1 complete sepa-ration of these fibers from :1 each lather. v

--It i is 'accordingly a one of 131-16 5 principal objects of the g present -invention to 1 provide :apparatus and :a -,method for 1 treating liquid --;s1urr-y stocks wherein. the ,stock to :be refined; 151631154X! to :pass between rotating cylindricalzbrushes under-such controlled:conditions-efw relative speeds and spacing ,zthat rsubstantially =eomplete separation of the individual:,fihers: =or othenparticles 'ispaccompli-shed in a sing-le :pass;

Another object, is {to .provide apparatus and a method for refiningdiquid-.slurry stocks :wherein the refining --.-power is applied: directly to .the individual fibers or other solid ear-tides in the Steele-,-rathersthanzto hundles or groups offibers, and wherein; all :the :2 solid material I in this stock is-;-caused to come in \working'. contactwith the workingssurtaces of the refining -,members with no opportunity; ionehanneling ,or bypassing.

additionalwohieetsiszto provide such an apparatus and method :wherein ,the solid material inqthe stock ,-is1eonceztratedv and;.-dewatered during working thereon ,torleilective separating action-land: iss them-remixed vwith the liquid; part-of the .stockxfor-efiectiveresuspensien as itis ,discharged, and-whereinrknots and; other undesired non-fibrous particles, lumps or the like, are passed:through-.Rwithout a comminutien'rand iwithoutr'damageto ,i'zheyappara,tus.

lt isa-alsoan'jobject'of-thei inventioneto provide refinin apparatus. I ;of -,the ,.-oharacter described i win-eh {is ssiiaaple x construct and to maintain,

acee, 165

33 which is economical of power and space in operation, and which is readily varied in its action in accordance with the desired characteristics of the refined stock.

Other objects and advantages will be apparent from the following description, the accompanying drawing and the appended claims.

In the drawing Fig. l is a view partly in elevation and partly in section on the line l-l of Fig. 2 showing refining apparatus constructed in accordance with the invention;

Fig. 2 is a side elevation, partly broken away and in section, of the apparatus of Fig. 1;

Fig. 3 is an enlarged and schematic view illustrating diagrammatically the action of the apparatus;

Fig. 4 is an enlarged fragmentary section on the line 44 of Fig. 2; and

Fig. 5 is a schematic view illustrating diagrammatically a combined refining and thickening operation in accordance with the invention.

Referring to the drawing, which illustrates a preferred embodiment of the invention, the base frame It supports a headbox H which receives the stock to be refined through an inlet connection I3, and which is provided with an overflow discharge connection l4 controlled by an adjustable overflow dam l5. A housing which is rectangular in horizontal section is mounted below the headbox II to receive the stock therefrom, and communication between the headbox and housing is controlled by a pair of laterally adjustable gates 22 having suitable handle rods 23 slidable in bushings 24 and provided with set screws 25 for holding the handles with the gates 22 in desired adjusted position. The housing 20 is adapted for connection at 26 to a suitable conduit or the like for receiving the discharged stock.

Within the upper end of the housing 20 and just below the gates 22 is a pair of cylindrical brushes 38 mounted on a pair of parallel shafts 32 and arranged with their adjacent surfaces in substantially touching or kiss contact relation to form a nip 33 which receives the stock flowing keyed to the shaft by means of the pin and.

slot arrangement indicated at 38. Satisfactory results have been obtained with the bristles 35 formed of thin wire, such as stainless steel wire & inch in diameter arranged with approximately 256 wires per square inch at the surface of the brush, and in order to assure that the outer ends of the bristles will be closely spaced, the length of the bristle is preferably comparatively short in comparison with the diameter of the core 34. For example, satisfactory results have been obtained with each of the bristles only about one inch in length in comparison with a diameter of eleven inches for the core.

Provision is made for supporting the shafts 32 in accurately parallel and spaced relation to maintainthe desired uniformly close relation-' shipof the brushes 33. Each shaft is of relatively large diameter for adequate stiifness and is supported in a pair of similarly large pillow blocks 40 adjustably mounted on the top of the base frame It! by means of bolts 4! in slots 42. As shown in Fig. 4, lugs 43 are welded to the top of the frame l0, and bolts 44 are threaded therethrough to engage the pillow block 40 on either side and thus to provide for laterally adjustable positioning of each of the pillow blocks in proper relation with the others to give the desired spaced alignment of the shafts 32 before the bolts 4! are tightened to hold the parts in the desired proper relation. The openings in the side of housing 26 are formed with sufficient clearance for shafts 32 to provide for such lateral adjustment as may be necessary, and fillets 4'5 are provided at each end of nip 33 and just inside the ends of the brushes 33 to serve as dams assuring proper guiding of the stock between the brushes, the lower edges of these fillets being curved as shown for a running fit with the surfaces of the brushes.

Each of the brushes 33' is shown as provided with a separate drive motor 50 and an adjustable speed drive. Each drive includes an intermediate shaft 5l carried by a frame 52 pivoted at 53 to the base It. .The frame 52 is adjustable about its pivot 53 by means of a screw 55 threaded through a swivel St on the frame and operated by a handle 57 through gearing indicated at 58. Each of the intermediate shafts 5| carries two axially fixed outer sheaves tit and an axially movable inner sheave ti, and the belts 32 and 63 connect these sheaves with the drive pulley 65 on the motor shaft and a pulley 66 on the shaft 32. Accordingly, when either of the shafts 5| is raised or lowered with its frame 52, the floating sheave 51 will be caused to move to the right or left respectively as viewed in Fig. 2, and the effective relative diameters of the intermediate sheaves are thus changed to vary the drive speed of the shaft 32 connected therewith.

In operation with this construction, the stock to be refined is supplied to the headbox II, and

" the gates 22 are adjusted to admit this stock to the nip 33 at a desired rate. Highly desirable results are obtained when the rate of approach flow to the nip is relatively slow in comparison with the peripheral speed of the brushes 3B, for example an approach flow of the order of 16 feet per second for stock at a consistency of approximately 4% by weight when the peripheral speed of the brushes is of the order of 200 feet per second. Under these conditions, it will be quickly therethrough, and also with the brushes arranged as shown in Figs. 1 and 2 in close fitting relation to the bottom of the headbox H and to the fillets 45, all of the stock passing through the gates 22 also passes through the nip of the brushes, since the effect of the rotation of the brushes at high speed is such as to inhibit bypassing of the stock around them.

Maximum effectiveness in refining or defibering action, as well as the minimum power requirements, have been obtained when the brushes are arranged and operated as described at the same relatively high rotational speed. Under these conditions, the individual bristles become substantially rigid as a result of centrifugal force, and with the peripheral speed of the brushes materially greater than the rate of approach flow of the stock to the nip 33, the ends of the bristles work against the comparative inertia of the pool of stock in the nip, which causes a brushing or drawing out action on the fibers before they reach the smallest part of the nip effective to separate the bundles or groups of fibers into their individual components.

Another result of a substantial speed differenseen that the stock entering the nip is drawnogeomrres sudden and vidlerit acceleration df the stock as it passes between the brushes which fur ther aids the-dies'ired separatingg action. AIsmssince the relative inertia of "the approach iiow provides =a drag on thefibers against whichtheaends of the bristtes =work, there is ra separating action :on the individual fibers*which is' siniilar to the efi'ect of teaslin'g-orraising themap on a blanket another rams, wit-h i the "individual fibers -bin'g Eliteially drawn or-dragged but ofsuspension- -by stapling over the 'rapidly nmving ends of the bristles. Furthermore,- this aibrading action-of *th'e bristle ends creates zones "of in'tense hydraulic {shear Whlh iui 'ther Raid the -desired "effect *of tearing apart the bundleser'lumpsof fibers.

addition to these actions on the stack as it approaches the nip $3, the "fibers *or oth'er *solid particles thierein are coneentrated in 'a th'in layer as they pass between' the brushes, as in'dicated diagrammatically at H! -in"=Fig. 3, since *With :Fthe bristles cl'o'sely packed an'dth'e brushes rdtating at -lilg'h=-sp'e'ed, there considerable resistance to penetration of the"brushes 'by=the 'fibers; cJn the other hand, the liquid comp'o-nen't O'f-th'e stock can flow throughthe spaces between the sides dfthe bristl'es,ias indieated at-l l in Fi'gnB; where is --'-thus a straining and dewat'ering' action on -the fibers as -they pass through-the nip of the' brushes, so thatithe brus'hinjg or tea'seling efieet f the ends oi the bi 'i's-tles is applied'direetly to the =i-ndividu'al 'fibers in an increa-singly -dewatered='-and c'cmp'aeted condition.

The thiekness ofithe layer lt of fibers depends upon the' rlative rspacing-iof fthe lbrushefs and optimum -"eifectiveness in clefibering action has been obtained when lthe ends-(ff -th'e bristles ar'e ln substantially kissmdfitact and the. spe'ed 'df rotation df the fbnrshes 'is uniformlyd'iigh. Under such conditionsthe e'fiective "thickness of *the layer approaches -the tl iiekne'ss of -the individual fibers, iand' the maximum work is done on each fiber. lit :greater i-spacin'g of t'he brushes, 'the action #Inay 'be less eflfective' for a single =pass through 'the device, -and if the' 'brushesare 'closer together, the -resulting rubbing action fdu'e to' intermeshing of the ends (if the 'bristles -causes undesirable wear andfriction.

invention accordingly provides a highly effective refining action which has the further adVantagddfieconcrri-ical eos'ti both in the producthin or ther'apparatu-s and 'm'ithei'operating cost andlpowernequirements. isin'ce aumf the istock i'scforeed it!) pass through the lnip df the rbrus'hes, it iis tall :subjecte'd substantially -';equally 'the efreetive tiforces zan'd there is in-o oppet-trinity 'Tfcr channeling such as can itak-e ipla'ce Kin-fa "j ordan type edit-refiner. 1 Also, ithe zpowe sis capplied rdireo-tly fto thezind'ividua'lifibers inrconeentratedmnd since it isk-131W possible to rremoversubstantially fiber omits outer surface.

all iusable ifiber from the knots "which may the present :without grinding :up'ithe knots 'tthemselves, which are readily removed by a suitable screen at a later stage in the refining system. The same'result is obtained wlth respect to pieces of .cellophane or the like, which :are passed through the nip substantially without disintegration and can thus be readily removed by-a-subsequent screening-step.

\ with the :brushes supported as LShQWn at th'e upper en'd of housingilll:and'thus abovathe liquid levebin thesh-ousing, the lower :part' of the housing formsa hamber open lto atmosphere 'atithe dischargesidebf thernip of the?brushes-vvhich provides an .*open :space JfOI free discharge of stock firom Cthe nip without back :pressure --such as would llfiSllll) if the'brushes were submerged, aand SlIlGBZthSStOCKiS thHS ableito attain ahigh speed in passing through :the ,nip of the irritating brushes, 1' it .is discharged relatively violently into the sopentlower part :of'the housing 20, and the fibers or other :paiiticles are thus thoroughly rremixedmith ithe liquid :component of "the stockzby thiszhighavelocity discharge. Effective ,resuspensi'on :of the fiber thus eflected substantially immediately, and'thestocbmayabe pipediawayif desired Y from the. lower end: ofwthe 'housingiill for furtherrefining or othertreatment. 'Inaddition, centrifugal force is particularly :,effective .at zthe pointzrof dischargerofthe stock fromthe .nip, since it :causes a ny fiber which .may have penetrated between the rbI-lSlllBS =to bBzthI'OWIl clear .into the lower part :of the housing. .Thu dnaadditionztn the other advantages of the apparatus, its natural action :in operation. isrsuch =as itorcause. continuous self-cleaning ;of' :the lbrushes.

:Eig; .15 :illustrates somewhat diagrammatically an arrangement #01? [apparatus .wherein the high velocity :of zthe discharge from :the :rotating brushes is :utilized for high speed thickening :of the stock after its passage between the :brushes. In Eig.:?5, thastock .to .be treated:is-shownvas conducted ibyz ar funnel J 5 E052. i-paiikof' rotating (cylindricaLbrush'es -71 of thesame general characteristics *and arrangement as described .-in connection with Figs. 1x130 3. -A .wireacovered roll is mountedibelow rth'e inip Of :the brushes to -;re-- ceive ;;the discharge therefrom gas indicated at B l. Thahighrspeed discharge fromithe brushes thusiimpinges-on the :roll BEL'SO that afilaigge proportiomgof theliquid component will be'thrown throughathe" wire coveredn'ollsurface, leaving the With the .roll 8!) r0 tating in-clockwise r direction as indicated {by the arrowzin 'gFig'. :5, :the liquid will be discharged indicated sat L82 and may be collected .andzrecirculated eas {required to trecover :=such fiberszas may :bef-rthitowntthroug'h the :vvire covered :sur-

faeeof the roll. wsimilarlyzthe. fiber wilkinilarge measure she fthrown olft from the atop :of ?.the roll 80' rinithe :opposite direction (as :indicated by pthe arrow fiap'andzthisrremoval :ofxafibersrfrom thei rroll v maybezfacilitatedtby aadoctorz'asindicatedgatifli.

The :apparatus tand'rmethod of ithe invention have been found particularly useful in connectionawithz the refiningof paperrmakingrstock, but theirnse is not limited to this-zfield and they are applicable ate the s.refining. of other Bliquid slurry stocks, iparticularly :rwhere high speed and lowsecst of-operation aredwirable, :andntheyioffer :simiiar advantages Bf "reflective sand :low cost refining for such purposes and may :be ;readily adapted ate the particuiarfconditions involvedfin SllGhfQhhel'zllsGS. accordingly, while xthezmethcds rand :forms 'zdf apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is: V

1. Apparatus for treating a liquid slurry stock comprising a pair of cylindrical brushes, means including a frame supporting said brushes for rotation with the axes thereof in predetermined spaced and parallel relation in substantially the same horizontal plane to locate adjacent surface portions thereof in close relation forming a horizontal nip adapted to receive said stock in vertical flow therethrough, means forming an inlet located substantially directly above and in line with said nip for supplying said stock in direct vertical fiow thereto, means controlling said supply flow of stock to said nip to a relatively slow rate of approach flow, drive means effective to rotate said brushes at a relatively high peripheral speed materially greater than said approach flow rate to draw said stock through said nip at a suddenly accelerated rate of flow for effective separation of the solid component of said stock into substantially individual particles and to discharge said separated stock with high centrifugal force substantially directly downwards, and means forming a chamber open to atmosphere below said nip to provide an open space for receiving said freely discharged stock from said nip.

2. Apparatus for treating a liquid slurry stock comprising a pair of cylindrical brushes, means including a frame supporting said brushes for rotation with the axes thereof in predetermined spaced and parallel relation in substantially the same horizontal plane to locate adjacent surface portions thereof in close relation forming a horizontal nip adapted to receive said stock in vertical flow therethrough, means forming an inlet located substantially directly above and in line with said nip for suppling said stock in direct vertical flow thereto, means controlling said supply flow of stool: to said nip to a relatively slow rate of approach flow, means confining the effective width of said inlet to substantially less than the distance between said brush axes to limit said approach flow of stock to a width not substantially greater than the minimum width of said nip, drive means effective to rotate said brushes at a relatively high peripheral speed iaterially greater than said approach flow rate to draw said stock through said nip at a suddenly accelerated rate of flow causing effective separation of the solid component of said stool; into substantially individual particles and maintaining said limited width of said approach flow in the upper portion of said nip, and means forming a chamber open to atmosphere below said nip to provide an open space for receiving said freely downward discharged stock from said nip.

3. Apparatus for treating fibrous paper making stock comprising a pair of cylindrical brushes, means including a frame supporting said brushes for rotation with the axes thereof in predeten miner. spaced and parallel relation in substantially the same horizontal plane to locate adjacent surface portions thereof in close relation forming a horizontal nip adapted to receive said stock in vertical flow therethrough, means forming an inlet located substantially directly above and in line with said nip for supplying said stock in a direct vertical flow not substantially greater than the minimum width of said nip, drive means efiective to rotate said brushes at a relatively high peripheral speed in the direction to draw said stock through said nip, means for maintaining the rate of said approach flow of stock materially lower than said peripheral speed of said brushes to establish a relative inertia effect on the stock entering said nip causing a teaseling action on the individual fibers therein by the more rapidly moving ends of the bristles on said brushes for effective separation of said fibers from each other, and means forming a chamber open to atmospheric pressure below said nip to provide an open space for free downward discharge of said stock from said nip.

4. Apparatus for treating fibrous paper making stock comprising a pair of cylindrical brushes, means including a frame supporting said brushes for rotation with the axes thereof in predeter mined spaced and parallel relation in substantially the same horizontal plane to locate adjacent surface portions thereof in close relation forming a horizontal nip adapted to receive said stock in vertical flow therethrough, means forming an inlet located substantially directly above and in line with said nip for supplying said stock in a direct vertical flow thereto at a relatively slow rate of approach ,fiow, means controlling said approach flow of stock to an effective width substantially less than the distance between said brush axes, drive means effective to rotate said brushes at a relatively high peripheral speed materially greater than said approach flow rate to produce a straining action on said stock causing the fibrous constituents thereof to be concentrated in a central layer with a reduced fibrous content in the layers on either side thereof, means forming a chamber open to atmospheric pressure below said nip for receiving free discharge of said stock from said nip, and said drive means being effective also to create a centrifugal force on said discharged stock suflicient for effective releasing thereof in said chamber;

5. Apparatus for treating a liquid slurry stock comprising a pair of cylindrical brushes, means including a frame supporting said brushes for rotation with the axes thereof in predetermined spaced and parallel relation in substantiallythe same horizontal plane to locate adjacent surface portions thereof in close relation forming a horizontal nip adapted to receive said stock in vertical flow therethrough, means forming an inlet located substantially directly above and in line with said nip for supplying said stock in direct vertical flow thereto, means controlling said supply fiow of stock to said nip to a relatively slow rate of approach flow, drive means effective to C rotate said brushes at a relatively high peripheral speed materially greater than said approach flow rate to draw said stock through said nip at a suddenly accelerated rate of flow for effective separation of the solid component of said 6 stock into substantially individual particles and said perforated surface while the liquid co'nstitu cuts of said stock passes into the interior of said roll, and means for rotating said perforate roll to effect discharge therefrom of said solid and liquid constituent in substantially the opposite direction.

6. The method of treating a liquid slurry stock which includes the steps of flowing said stock directly downwardly into the horizontal nip formed by a pair of brush rolls having the axes thereof in spaced and parallel relation in substantially the same horizontal plane, limiting the supply now of said stock to said nip to an effective width substantially less than the distance between said brush axes, controlling the rate of approach flow of said stock to a relatively slow rate, and rotating said brushes at a relatively high peripheral speed materially greater than said approach flow rate to draw said stock through said nip at 2. suddenly accelerated rate of flow causing effective separation of the solid component of said stock into substantially individual particles followed by substantially directly downward discharge of said stock from said nip.

7. The method of defibering paper making stock which includes the steps of flowing said stock directly downwardly into the horizontal nip formed by a pair of cylindrical brushes having the axes thereof in spaced and parallel relation in substantially the same horizontal plane, rotating said brushes at a relatively high peripheral speed in the direction to draw said stock through said nip, limiting the supply flow of said stock to said nip to an effective width substantially less than the distance between said brush axes, controlling the rate of said supply fiow of stock to said nip to a rate materially lower than said peripheral speed of said brushes to establish a relative inertia effect on the stock entering said nip causing a teaseling action on the individual fibers therein by the more rapidly moving ends of the bristles on said brushes for effective separation of said fibers from each other, and maintaining the discharge side of said nip open and for free downward discharge of said stock therefrom to promote maximum acceleration of said stock in passing through said nip.

8. The method of defibering paper making stock which includes the steps of flowing said stock to a working station at a relatively slow rate of approach flow, suddenly accelerating the rate of flow of said stock at said station and simultaneously effecting laminar flow thereof to create zones of hydraulic shear therein, dewatering said stock and concentrating the fibers thereof in a relatively thin layer substantially simultaneously with said acceleration step, mechanically working said concentrated fibers to effect separation of the individual said fibers from each other, and thereafter discharging said stock from said working station with suflicient violence to effect thorough remixing of said fibers with the liquid component of said stock.

9. The method of deflbering paper making stock which includes the steps of flowing said stock directly downwardly into the horizontal nip formed by a pair of cylindrical brushes having the axes thereof in spaced and parallel relation in substantially the same horizontal plane, limiting the supply flow of said stock to said nip to an effective width substantially less than the distance between said brush axes, rotating said brushes at a relatively high peripheral speed downwardly through said nip to produce a straining action on said stock causing the fibers therein to be concentrated in a central layer surrounded on either side by essentially liquid layers, and discharging said stock freely downwardly from said nip into a chamber open to atmospheric pressure to cause thorough remixing of said fibers and said liquid.

10. The method of defibering and thickening paper making stock which includes the steps of flowing said stock directly downwardly into the horizontal nip formed by a pair of cylindrical brushes having the axes thereof in spaced and parallel relation in substantially the same horizontal plane, limiting the supply flow of said stock to said nip to an effective width substantially less than the distance between said brush axes, controlling the rate of approach flow of said stock to a relatively slow rate, rotating said brushes at a relatively high peripheral speed materially greater than said approach flow rate to draw said stock through said nip at a suddenly' accelerated rate of flow causing effective separation of the individual fibers in said stock, discharging said accelerated stock directly downwardly from said nip upon the surface of a perforated roll to cause concentration of said fibers on the surface of said roll while the liquid component of said stock passes into the interior of said roll, and continuously rotating said roll to effect discharge of said fibers and said liquid in opposite directions while continuously presenting a clean surface of said roll to said discharged stock.

JOSEPH BAXTER, JR.

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